Amplifying system



Feb. 10, 1931. ,w. YCARLSON E'TAL AMPLI-FYING SYSTEM Filed Jan, 28, 1927 Fig 2.

Fig.3.

Fig.4.

, Inventor-s:

'Wendell Carlson,

Ralph 5. Holmes, by a Their-- A'ttobngy Fatented Feb. 10, 1931 UNITED STATES PATENT OFFICE WENDELL L. CABLSON' AND RALPH S. HOLMES, O]? SCHENECTADY, NEW YORK, AS-

SIGNOBS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK AMPLIFYING SYSTEM Application filed January 28, 1927. Serial No. 164,341.

Our invention relates to systems wherein electrical impulses are amplified through means comprising a plurality of interconnected space discharge devices, such as thermionic amplifiers or the like, and has for its rincipal object the provision of an ampliying system which may be operated over a wide range of frequencies with a uniformly high de cc of selectivity and with uniform ampli cation.

Our invention will be better understood from the following description when considered in connection with the accompanying drawings and its scope will be pointed out in the ap ended claims.

Referring to the drawings, Figs. 1 to 3 1llustrate amplifying systems wherein our invention has been embodied; and Fig. 4 shows a plurality of curves relating to t e operation. of these systems.

Fig. 1 illustrates an amplifying system comprising spacedischarge devices 1 and 2 each provided with a cathode 3, an anode 4, a control grid 5, and a screen grid 6 which is arranged to practically eliminate the capacitative coupling between the control'grid 5 and the anode 4. Suitable sources of 0- tential, such as batteries 7, are provided or maintaining the screen grids 6 at predetermined potentials with respect to the cathodes 3 and like sources 8 are connected in the input circuits of the devices 1 and for biasing the control grids 5 to potentlals whlch ensure proper operation of these devlces. Terminals 9 and 10 are provided for connecting the input circuit of the device 1 to the source of the electrical impulses which are to be am lified. Current is supplied to the output circuits of the devices 1 and 2 from sources 11 and 12.

It will be observed that the output circuit of the device 1 is coupled to the input circuit of the device 2 through a capacitative coupling 13 and an inductive coupling 14 which are preferably 180 out of phase with one another; that an inductance 15 and a capacity 16 are provided for tuning the output circuit of the device 1; and that an inductance 17 and a capacity 18 are provided for tuning the input circult of the device 2.

In the present example, the capacitive coupling is provided between the high potential ends of said tuned circuits and the inductive couplin is provided at the low potential ends. 'lhe inductive coupling predominates and is opposed increasingly with frequency .by the capacitive coupling which increases at a higher rate as will be seen hereinafter. The advantages of this combination of capacitative and inductive coupling between two tuned circuits will be readily understood upon consideration of Fig. 4. Such tuned circuits may not necessarily be provided between two electric discharge devices but may be any tuned circuits coupled in the same manner and for the same purpose.

Fig. 4 shows a curve a which indicates the effect of change in frequency on the amplitica tion ratio from the input of tube 1 to the input of tube 2 when only the magnetic or inductive coupling 14 is used. Curve 5 shows the relation between frequency and the amplification ratio when only the capacitative coupling 13 is used. Curve 0 is the resultant of curves a and b. This resultant curve indicates the effect of change in frequency on the amplification ratio when both the capacitative coupling 13 and the -inductive coupling 14 are used with the capacity coupling 180 out of phase with the magnetic coupling. It will be observed that both couplings increase with frequency, and that the amplification ratio is substantially constant over a considerable range of frequencies and that the coupling tends to be lower at the higher frequency end of the range. The tuning of both the output circuit of the device 1 and the input circuit of the device 2 to the frequency of the impulses to be amplified has the marked advantage that only impulses having a frequency within the range of substantially uniform amplification are selected.

The screen grid tube possesses a very high impedance and accordingly it is possible to utilize a high impedance output circuit. The screen grid prevents coupling between the input and output circuits. This is advantageous because the tuning of the output circuit and the use of the compound coupling ed to the coil 15 and the coupling :3}, e. povided for neutralizing the capacitativc coupling between the control grid 5 and the anode l oi the device 1.

Fig. 3 illustrates an. ampliryi system which differs from that of Fig. .1. only in that the neutralizing condenser and coil control grid 4. It will be apparent tha any I us other than those iilusrrated ..o 3 may be pmvided for neutrab icin t" capacitative coupling between the control grid 5 and the anode a; and that the advantages of the compound capacitutive and inductive coupling between the two tuned circuits are not limited to the particular systems illustrated.

The embodiments of the invention illustrated and described herein have been selected for the purpose of clearly setting forth the principles involved. It wi l be ap rent. however, that the invention is susceptible of being modified to meet the dilierent conditions encountered in its use and we therefore aim to cover by appended claims all modifications within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1.. The combination of a pair of space discharge devices including input and output circuits, means for tuning the output circuit of one of said devices and the input circuit of the other of said devices, and ca acitative and inductive couplings connecte between said tuned circuits, said couplings being out of phase with each other and the capacitive coupling being between the high potential ends of said tuned circuits.

2. The combination of a pair of space discharge devices each provided with an input circuit including a cathode and control grid and with an output circuit including a cathode and anode, means for tuning the output circuit of one of said devices and the input circuit of another of said devices, and a coupling including a capacity and an inductance each coupled separately and independently between said tuned circuits and arranged to with one ano in, i J located betwen the high potential ends of said tuned circuits.

3. The combination of psi charge devices each provided circuit and win ode V output P circuit 02 one. cl and the input circuit of the other oi said devices, a com pound ce eeitative and inductive coupling connected between said tuned circuits, the capacitive and inducti e componen s thereof being arranged separu dc v0ltages in said tuned input -ich are substantially 180 out oi with each other, and means including a s ,c-n grid as sociated ilh said output ci cuit for prevent ing capacitive coupling between said output circuit and the control electrode of the device connected with said output circuit.

2.. The combination of a. pair of space discharge devices comprisinginput and output circuits, means for tuning the output circuit of one of said devices and the input circuit of the other of said devices, and said circuits being capacitively and inductively coupled, the inductive coupling predominating and being in opposition to the capacitive coupling.

The combination of a pair of space discharge devices comprising input and output circuits, means for tuning the output circuit of one of said devices and the inputcircuit of the other of said devices to the same frequency, and said circuits being capacitively and inductively coupled, the inductive coupling predominating and being in opposition to the capacitive coupling.

6. In a multistage alternating current arnplifier system, an interstage coupling means therefor providing capacitive and inductive coupling between said stages, the capacitive no coupling being substantially 180 out of phase with the inductive coupling and both eing adjusted so that the amplification ratio is rendered substantially uniform over a relatively wide range of frequencies, said adjustment being such that the inductive cou-. pling predominates and that the capacitive iii an input iprisin :1 cathode and control grid 'rc it" a cathftlll coupling increases more rapidly with frewcam substantially constant over a relatively wide range of fre uencies.

8. A coup ing means for interconnected high frequency circuits, said means including an input circuit and an output circuit, means for tuning said circuits to the same frequency, said circuits being inductively coupled at their low potentiai ends, and being capacitively coupled at their high potential ends in opposing phase relation to said inductive coupling.

9. The combination with a pair of electric dischar e amplifier devices, of a-coupling means t erefor, said means including a tuned input circuit for one of said devices, a tuned output circuit for the other of said devices, said circuits being inductively coupled, and being capacitively coupled in opposing phase relation to said inductive coupling, and means associated with said output circuit for preventing capacitive coupling therewith thrgugh the device with which it is associate a 10. The combination with a pair of electric dischar e amplifier devices, of a coupling means t erefor, said means including an in put circuit for one of said devices, an output circuit for the other of said devices, means for tuning said circuits to the same frequency, said circuits being inductively coupled, and bein capacitively coupled in opposing phase re ation to said inductive coupling. said inductive and capacitive couplings both being arranged to increase with frequency, and said capacitive coupling being arranged to increase with fre uency more rapidly than said inductive coup ing.

In Witness whereof, we have hereunto set our hands this 27th day of January, 1927. WENDELL L. GARLSON. RALPH S. HOLMES. 

